The impact wrench isn’t a must-have automotive tool, but it’s definitely a really-would-like-to-have. Also known as an air gun, a torque gun, or “that loud thing pit crews use to undo wheel nuts real fast,” the impact wrench’s rotating hammer knocks on its output shaft to make quick work of twisting bolts. Plus, it lets onlookers know that you are a harnesser of potent earthly forces. Traditionally powered by compressed air, impact wrenches have entered the portable electric era. To see how tough 18-volt battery-powered wrenches are, we rounded up seven half-inch-drive units of various sizes and strengths. Even the weakest tool here can easily handle the roughly 100 pound-feet of torque required to remove a lug nut. Now go forth and wrench.

Unless noted, each kit includes a charger and two lithium-ion batteries.

Lightest of the big wrenches, the Bosch is as smooth as Billy Dee Williams. It even emits the most dulcet tones. Our calibration torque wrench was limited to 600 pound-feet, and loosening bolts torqued to that rating took more than a few seconds, suggesting that that’s about the Bosch’s limit. As noted, hammering vibration is minimal, lessening hand fatigue. Like the other biggies, the Bosch stays cool during repeated use. Flag-wavers take note: The Bosch is assembled in the U.S.A. (boschtools.com)

The monster Makita is big and heavy, but it’s also the strongest wrench we tested. It unwound 600-pound-feet bolts with ease after only a few seconds of hammering. It transmits more vibration than the Bosch, but the Makita’s battery is isolated from the rest of the wrench to prevent damage caused by mechanical shock. And like the DeWalt, it uses a single-speed forward/reverse trigger. (makita.com)

The pin that holds attachments to the DeWalt is cylindrical, not tapered, which helps to better secure sockets. We also like the two-way forward/reverse trigger, although speed is not adjustable. The other big wrenches have an easier time with the high-torque bolts; the DeWalt took up to 15 seconds to get the job done. The rear of the wrench sometimes rests on the top of your hand, diminishing comfort. (dewalt.com)

* Includes two nickel-cadmium batteries and charger. A kit with two lithium-ion batteries costs $399.

The Hitachi has two speeds, “power” and “save.” We used the former mode for this test. Lightest of the group, the Hitachi is surprisingly powerful. It also has a combination LED light/belt clip. Our only complaints are a lipless trigger, which is a definite finger irritator, and the lack of a rubberized grip. (hitachipowertools.com)

Cordless impact wrenches generally demand a trade-off between power and comfort. The Milwaukee favors the latter, with the best ergonomics of the group, a grippy rubberized bottom, and minimal vibration. That said, it’s the weakest in loosening torque, and it produced the poorest test results. Bonus point: The battery has a four-light charge meter. (milwaukeetool.com)

Ideal for amateurs, the affordable Craftsman straddles the line between the powerful big wrenches and the light smaller ones. A rubberized handle makes it one of the most comfortable wrenches, but the unit gets hot and performance degrades during repeated use. We should note that the Craftsman battery is advertised at 19.2 volts but registered more than 20 volts on a test meter. (craftsman.com)

The Ryobi and the Craftsman are near clones, but the Ryobi has a slightly smaller grip for those with diminutive hands. More than once during our testing, the Ryobi’s battery vibrated loose enough to prevent the wrench from working. A quick removal and remounting of the battery fixed the symptom but not the cause; the battery should clip into place more securely. (ryobitools.com)

* Items sold separately. Price includes wrench, charger, and one battery.